1995 Chevy Truck Running Poorly

Hey Guys, Need some help here A Buddy of mine has a 1995 K1500 Ex.Cab 5.7 TBI Truck With about 179,000 miles on it and about two days ago it just started to run like shit if im easy on the throttle it will rev up. but if I punch the gas it acts like its getting too much fuel Bogs down and it will even back fire up through the TBI (With Flame). when the truck is running the exhaust smells VERY VERY Rich. (as rich as a carb Engine) here is what my buddy has replaced lately in the past 2 days Plugs & wires (one wire at a time) new Fuel Filter, New Engine coolant temp sensor up by the thermostat. My buddy was thinking it was a plugged cat or bad O2 Sensor I told him if it was the sensor it would throw a code So I went under and unplugged the o2 sensor and told him to start the truck it ran worse so it wasn’t the o2. then I unplugged various plugs on the engine to see if it would make any difference and every plug I tried it would stall the engine or rev the engine up. (Also there is NO Check engine light either) im wondering if it isn’t the TPS sensor But im not sure I was originally thinking it was the fuel pressure regulator but the raw fuel smell is telling me a different story.. im stumped can anyone tell me what could possibly be going on here.